Method of Manufacturing Semiconductor Device and Non-transitory Computer-readable Recording Medium

ABSTRACT

According to one aspect of the technique, there is provided a method of manufacturing a semiconductor device, including checking a leak from a process furnace before a substrate is processed. The checking includes: (a) measuring, by a partial pressure sensor provided at an exhaust pipe, an oxygen partial pressure value of a residual oxygen after the process furnace is vacuum-exhausted; (b) comparing the oxygen partial pressure value measured by the partial pressure sensor with a threshold value; and (c) when the oxygen partial pressure value is higher than the threshold value in (b), performing at least one among: purging the process furnace and evacuating the process furnace.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/JP2018/035012, filed on Sep. 21, 2018, the entire contents of whichare hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a method of manufacturing asemiconductor device and a non-transitory computer-readable recordingmedium.

BACKGROUND

In a substrate processing apparatus configured to process a wafer(hereinafter, also referred to as a “substrate”) under a decompressedenvironment, a leak check of a furnace of the substrate processingapparatus is performed during a setup operation of the substrateprocessing apparatus. For example, as the leak check of the furnace,whether or not a gas is leaking from the furnace is checked. Forexample, according to some related arts, a leak check technique ofdetermining whether to proceed to the next step (film-forming step)according to a severity (leak amount) of a leak check error isdescribed. Further, according to a leak check method (build-up method),an inner pressure of the furnace is decompressed from the atmosphericpressure to a reference pressure, an exhaust valve of the substrateprocessing apparatus is closed when the reference pressure is reachedand maintained, and a pressure increment value of the inner pressure ofthe furnace is measured after the exhaust valve is closed. According tothe leak check method, both of the reference pressure and the pressureincrement value are determined by using a total pressure. Therefore, itis difficult to determine a relative amount of oxygen or an oxygencompound contained in an inner atmosphere of the furnace. Further, evenwhen the film-forming step is performed under the same conditions, it isindeterminate whether the resulting product would be acceptable ordefective.

As a method of measuring a partial pressure of a residual gas in vacuum,a quadrupole mass spectrometer may be used. When measuring the partialpressure at a pressure of about several Pascal (Pa), a measurement fieldfor the quadrupole mass spectrometer should be maintained in a highvacuum using a differential exhaust system. In order to secure the highvacuum of the measurement field, a pump such as a turbo molecular pumpis to be used. Thus, a system including the substrate processingapparatus becomes complicated and expensive, and there are many problemsin permanently installing the pump such as the turbo molecular pump inthe substrate processing apparatus. For example, a test wafer may beinserted into the furnace in order to check an oxidation degree in thefurnace. However, since the test wafer is transferred into the furnace,it may cause a delay in the setup operation of the substrate processingapparatus.

SUMMARY

Described herein is a technique capable of measuring a partial pressureof a gas, which causes a wafer to be oxidized before a film formation,such as a residual gas and a desorbed gas in a process furnace.

According to one aspect of the technique of the present disclosure,there is provided a method of manufacturing a semiconductor device,including: (A) checking a leak from a process furnace before a substrateis processed, wherein (A) includes: (a) measuring, by a partial pressuresensor provided at an exhaust pipe, an oxygen partial pressure value ofa residual oxygen after the process furnace is vacuum-exhausted; (b)comparing the oxygen partial pressure value measured by the partialpressure sensor with a threshold value; and (c) when the oxygen partialpressure value is higher than the threshold value in (b), performing atleast one among: purging the process furnace and evacuating the processfurnace.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a vertical cross-section of a substrateprocessing apparatus preferably used in one or more embodimentsdescribed herein.

FIG. 2 schematically illustrates an exemplary functional configurationof a leak check of the substrate processing apparatus preferably used inthe embodiments described herein.

FIG. 3 schematically illustrates a pressure curve when the substrateprocessing apparatus preferably used in the embodiments described hereinis vacuum-exhausted.

FIG. 4 schematically illustrates a process flow including a leak checkstep preferably used in the embodiments described herein.

FIG. 5 schematically illustrates a relationship between a waferoxidation index and a partial pressure of oxygen preferably used in theembodiments described herein.

FIG. 6 schematically illustrates an exemplary evaluation configurationof acquiring a correlation between a minute leak and a wafer oxidationpreferably used in the embodiments described herein.

FIG. 7 is a flowchart schematically illustrating the leak check steppreferably used in the embodiments described herein.

FIG. 8 is a flowchart schematically illustrating a leak check steppreferably used in a modified example of the embodiments describedherein.

DETAILED DESCRIPTION Embodiments

Hereinafter, one or more embodiments (also simply referred to as“embodiments”) according to the technique of the present disclosure willbe described with reference to FIGS. 1 through 8.

(1) Configuration of Substrate Processing Apparatus

Hereinafter, an exemplary configuration of a substrate processingapparatus preferably used in the embodiments will be described withreference to the drawings. Like reference numerals represent likecomponents in the drawings, and redundant descriptions related theretowill be omitted. In the drawings, for the sake of convenience of thedescriptions, features such as a width, a thickness and a shape of eachcomponent may be schematically illustrated as compared with actualfeatures. However, the drawings are merely examples of the embodiments,and the embodiments according to the technique of the present disclosureare not limited thereto.

Outline of Substrate Processing Apparatus

The substrate processing apparatus described herein as an example isconfigured to perform a substrate processing such as a film-formingprocess, which is part of manufacturing processes of a semiconductordevice. For example, the substrate processing apparatus is configured asa vertical type substrate processing apparatus (hereinafter, also simplyreferred to as “processing apparatus”) 2 capable of batch-processing aplurality of substrates.

Reaction Tube

As shown in FIG. 1, the processing apparatus 2 includes a reaction tube10 of a cylinder shape. For example, the reaction tube 10 is made of aheat and corrosion resistant material such as quartz and silicon carbide(SiC).

A process furnace 14 in which a wafer W serving as a substrate isprocessed is provided in the reaction tube 10. A heater 12 serving as aheating apparatus (heating structure) is installed on an outer peripheryof the reaction tube 10. The heater 12 is configured to heat the processfurnace 14.

Further, nozzles 44 a and 44 b described later are installed in thereaction tube 10. A temperature detector (not shown) as a temperaturedetecting structure is installed vertically along an outer wall of thereaction tube 10.

A manifold 18 of a cylinder shape is connected to a lower end opening ofthe reaction tube 10 via a seal 20 such as an O-ring. The manifold 18 isconfigured to support a lower end of the reaction tube 10. For example,the manifold 18 is made of a metal such as stainless steel. A lower endopening of the manifold 18 is opened or closed by a lid 22 of a diskshape. For example, the lid 22 is made of a metal. The seal 20 such asthe O-ring is provided on an upper surface of the lid 22 so that aninner atmosphere of the reaction tube 10 is hermetically (airtightly)sealed from an outside atmosphere. A heat insulator 24 is placed on thelid 22. There is provided a hole (not shown) elongated vertically at acenter of the heat insulator 24. For example, the heat insulator 24 ismade of quartz.

Process Furnace

As described above, the process furnace 14 provided inside the reactiontube 10 is configured to process the wafer W serving as the substrate.Thus, the process furnace 14 is configured such that a boat 26 servingas a substrate retainer is accommodated in the process furnace 14. Forexample, the process furnace 14 is made of a heat and corrosionresistant material such as quartz and SiC, and is formed as a singlebody.

Boat

The boat 26 serving as a substrate retainer and accommodated in theprocess furnace 14 is configured to support a plurality of wafersincluding the wafer W (for example, 25 to 150 wafers) in the verticaldirection in a multistage manner. For example, the boat 26 is made of amaterial such as quartz or SiC.

The boat 26 is supported above the heat insulator 24 by a rotating shaft28 passing through the lid 22 and the heat insulator 24. For example, amagnetic fluid seal (not shown) is provided at a portion of the lid 22where the rotating shaft 28 penetrates the lid 22. The rotating shaft 28is connected to a rotator 30 installed below the lid 22. Thereby, theboat 26 is rotatably supported by the rotator 30 while maintaining aninner atmosphere of the process furnace 14 to be hermetically sealed.

The lid 22 is moved upward or downward in the vertical direction by aboat elevator 32 serving as an elevator. Thereby, by jointly elevatingor lowering the boat 26 and the lid 22 in the vertical direction by theboat elevator 32, the boat 26 is transferred (loaded) into ortransferred (unloaded) out of the process furnace 14 provided inside thereaction tube 10.

Gas Supplier

The processing apparatus 2 includes a gas supplier 34 serving as a gassupply system. The gas supplier 34 is configured to supply gases usedfor the substrate processing to the boat 26 accommodated in the processfurnace 14. The gases supplied by the gas supplier 34 may be changeddepending on a type of a film to be formed. According to theembodiments, for example, the gas supplier 34 includes a source gassupplier, a reactive gas supplier and an inert gas supplier.

The source gas supplier includes a gas supply pipe 36 a connected to asource gas supply source (not shown). A mass flow controller (MFC) 38 aserving as a flow rate controller (flow rate controlling structure) anda valve 40 a serving as an opening/closing valve are sequentiallyprovided at the gas supply pipe 36 a in this order from an upstream sideto a downstream side of the gas supply pipe 36 a. The gas supply pipe 36a is connected to the nozzle 44 a which penetrates a sidewall of themanifold 18. The nozzle 44 a is of a tubular shape (pipe-shaped)extending vertically. The nozzle 44 a is provided with a verticallyelongated slit 45 a serving as a gas supply port opening toward theplurality of the wafers including the wafer W supported by the boat 26.A source gas supplied by the source gas supplier described above isdiffused through the slit 45 a of the nozzle 44 a, and then supplied tothe plurality of the wafers including the wafer W.

The reactive gas supplier is configured similarly to the source gassupplier. That is, the reactive gas supplier includes a gas supply pipe36 b connected to a reactive gas supply source (not shown), a mass flowcontroller (MFC) 38 b and a valve 40 b. The reactive gas supplied by thereactive gas supplier from the reactive gas supply source is supplied tothe plurality of the wafers including the wafer W through the nozzle 44b. The nozzle 44 b is of a tubular shape (pipe-shaped) extendingvertically. The nozzle 44 b is provided with a plurality of gas supplyholes (not shown) opening toward the plurality of the wafers includingthe wafer W supported by the boat 26.

The inert gas supplier includes gas supply pipes 36 c and 36 d connectedto the gas supply pipes 36 a and 36 b, respectively, and mass flowcontrollers (MFCs) 38 c and 38 d and valves 40 c and 40 d provided atthe gas supply pipes 36 c and 36 d, respectively. An inert gas suppliedby the inert gas supplier from an inert gas supply source (not shown) issupplied to the plurality of the wafers including the wafer W throughthe nozzles 44 a and 44 b. The inert gas serves as a carrier gas or apurge gas.

The inert gas supplier further includes a gas supply pipe 36 epenetrating the lid 22 and a mass flow controller (MFC) 38 e and a valve40 e provided at the gas supply pipe 36 e. The inert gas supplied by theinert gas supplier from the inert gas supply source (not shown) issupplied into the reaction tube 10 in order to prevent the gas such asthe source gas and the reactive gas supplied into the process furnace 14from flowing into the heat insulator 24.

Exhauster

An exhaust pipe 46 is provided at the reaction tube 10. A vacuum pump 52serving as a vacuum exhaust apparatus is connected to the exhaust pipe46 through a pressure sensor 48 and an APC (automatic pressurecontroller) valve 50. The pressure sensor 48 serves as a pressuredetector (pressure detecting structure) configured to detect an innerpressure of the process furnace 14, and the APC valve 50 serves as apressure regulator (pressure adjusting controller). With such aconfiguration, it is possible to adjust the inner pressure of theprocess furnace 14 to a process pressure suitable for the substrateprocessing.

Controller

A controller 100 is electrically connected to and controls the rotator30, the boat elevator 32, the MFCs 38 a through 38 e and the valves 40 athrough 40 e of the gas supplier 34 and the APC valve 50. For example,the controller 100 is embodied by a microprocessor (computer) with a CPU(Central Processing Unit), and is configured to control the operationsof the processing apparatus 2. An input/output device 102 such as atouch panel is connected to the controller 100.

A memory 104 serving as a recording medium is connected to thecontroller 100. A control program for controlling the operations of theprocessing apparatus 2 or a program (also referred to as a “recipeprogram”) for controlling the components of the processing apparatus 2according to the process conditions to perform a processing is readablystored in the memory 104.

The memory 104 may be embodied by a built-in memory (such as a hard diskand a flash memory) of the controller 100 or a portable externalrecording apparatus (for example, magnetic tapes, magnetic disks such asa flexible disk and a hard disk, optical disks such as a CD and a DVD,magneto-optical disks such as an MO, and semiconductor memories such asa USB memory and a memory card). The program may be provided to thecomputer using a communication means such as the Internet and adedicated line. The program such as the recipe program may be read fromthe memory 104 by an instruction such as an input from the input/outputdevice 102. The processing apparatus 2 performs a desired processingaccording to the recipe program under the control of the controller 100when the controller 100 executes the recipe program.

(2) Substrate Processing

Subsequently, as an example of the substrate processing, a basicsequence of a process (also referred to as the “film-forming process”)of forming a film on the wafer W serving as the substrate using theabove-described processing apparatus 2 will be described. Thefilm-forming process is part of the manufacturing processes in a methodof manufacturing a semiconductor device. Hereinafter, the film-formingprocess will be described by way of an example wherein a silicon nitride(SiN) film is formed on the wafer W by supplying HCDS (Si₂Cl₆:hexachlorodisilane) serving as the source gas and ammonia (NH₃) gasserving as the reactive gas to the wafer W. In the followingdescription, the controller 100 controls the operations of components ofthe processing apparatus 2.

Wafer Charging and Boat Loading Step

When processing the wafer W, firstly, the plurality of the wafersincluding the wafer W are charged into the boat 26 (wafer chargingstep).

After the plurality of the wafers including the wafer W are charged intothe boat 26 (wafer charging), the boat 26 is loaded into the processfurnace 14 by the boat elevator 32 (boat loading step). Then, the lid 22air-tightly seals the lower end opening of the reaction tube 10.

Pressure and Temperature Adjusting Step

After the wafer charging and boat loading step is completed, in thepressure and temperature adjusting step, the vacuum pump 52vacuum-exhausts (depressurizes and exhausts) the inner atmosphere of theprocess furnace 14 until the inner pressure of the process furnace 14reaches and is maintained at a predetermined pressure (vacuum level)(pressure adjusting step). The inner pressure of the process furnace 14is measured by the pressure sensor 48, and the APC valve 50 isfeedback-controlled based on the measured pressure information. Theheater 12 heats the process furnace 14 until the temperature of thewafer W in the process furnace 14 reaches and is maintained at apredetermined temperature. In the pressure and temperature adjustingstep, the state of the electric conduction to the heater 12 isfeedback-controlled based on the temperature information detected by thetemperature detector (not shown) so as to obtain a desired temperaturedistribution of the inner temperature of the process furnace 14(temperature adjusting step). The rotator 30 starts to rotate the boat26 and the plurality of the wafers including the wafer W accommodated inthe boat 26.

Film-Forming Process

After the temperature of the process furnace 14 is stabilized at apre-set process temperature, the film-forming process is performed onthe wafer W in the process furnace 14 after a leak check step describedin detail later is performed. The film-forming process (also referred toas a “film-forming step”) is performed by performing a source gas supplystep, a source gas exhaust step, a reactive gas supply step and areactive gas exhaust step.

Source Gas Supply Step

First, the HCDS gas is supplied to the wafer W in the process furnace14. A flow rate of the HCDS gas is adjusted to a desired flow rate bythe MFC 38 a. The HCDS gas whose flow rate is adjusted is supplied intothe process furnace 14 via the gas supply pipe 36 a and the nozzle 44 a.

Source Gas Exhaust Step

Subsequently, the supply of the HCDS gas is stopped, and the vacuum pump52 vacuum-exhausts the inner atmosphere of the process furnace 14. Inthe source gas exhaust step, N₂ gas serving as the inert gas may besupplied into the process furnace 14 through the inert gas supplier(purge by inert gas).

Reactive Gas Supply Step

Subsequently, the NH₃ gas is supplied to the wafer W in the processfurnace 14. A flow rate of the NH₃ gas is adjusted to a desired flowrate by the MFC 38 b. The NH₃ gas whose flow rate is adjusted issupplied into the process furnace 14 via the gas supply pipe 36 b andthe nozzle 44 b.

Reactive Gas Exhaust Step

Subsequently, the supply of the NH₃ gas is stopped, and the vacuum pump52 vacuum-exhausts the inner atmosphere of the process furnace 14. Inthe reactive gas exhaust step, the N₂ gas may be supplied into theprocess furnace 14 through the inert gas supplier (purge by inert gas).

By performing a cycle including the four steps described above apredetermined number of time (one or more times), it is possible to formthe SiN film with a predetermined composition and a predeterminedthickness on the wafer W.

Boat Unloading and Wafer Discharging Step

After the SiN film with the predetermined composition and thepredetermined thickness is formed, the N₂ gas is supplied by the inertgas supplier to replace the inner atmosphere of the process furnace 14with the N₂ gas, and the inner pressure of the process furnace 14 isreturned to the atmospheric pressure. The lid 22 is then lowered by theboat elevator 32 and the boat 26 is unloaded out of the reaction tube 10(boat unloading step). Thereafter, the processed wafers including thewafer W are discharged from the boat 26 (wafer discharging step).

For example, the process conditions for forming the SiN film on thewafer W are as follows:

Process temperature (the temperature of the wafer): 300° C. to 700° C.;

Process pressure (the inner pressure of the process furnace): 1 Pa to4,000 Pa;

Flow rate of the HCDS gas: 100 sccm to 10,000 sccm;

Flow rate of the NH₃ gas: 100 sccm to 10,000 sccm; and

Flow rate of the N₂ gas: 100 sccm to 10,000 sccm.

By selecting suitable values within the process conditions describedabove, the film-forming process can be performed properly.

(3) Leak Check Step

Subsequently, the leak check step performed before the film-formingprocess will be described. In the following description, the controller100 controls the operations of components of the processing apparatus 2for performing the leak check step.

The leak check step refers to a step of checking a leak from the processfurnace 14 that performs the film-forming step before the processfurnace 14 performs the film-forming step which is the substrateprocessing of processing the wafer W.

In order to perform the leak check step, the processing apparatus 2includes a configuration shown in FIG. 2. That is, for example, theprocessing apparatus 2 may include: the process furnace 14 capable offorming the film by supplying a process gas (for example, the source gasand the reactive gas) while mounting the wafer W such as a siliconsubstrate on the boat 26 in a multistage manner and heating the wafer Wby the heater 12; the gas supplier 34 configured to supply the processgas to the process furnace 14; the exhaust pipe 46 configured to exhaustthe gas such as the process gas after the film-formation process fromthe process furnace 14. The exhaust pipe 46 is provided with thepressure sensor 48 configured to detect the inner pressure of theprocess furnace 14, and the pressure sensor 48 continuously detects theinner pressure of the process furnace 14 from the pressure adjustingstep (after the boat loading step) until a vacuum level checking step(before the film-forming process) and a pressure control step (duringthe film-forming process).

The exhaust pipe 46 is provided with a partial pressure sensor 60capable of measuring a partial pressure of oxygen or a partial pressureof an oxygen compound in the vicinity of the pressure sensor 48. As thepartial pressure sensor 60, for example, a zirconia type oxygenconcentration meter or a cold cathode gauge capable of measuring apartial pressure of the gas by measuring a discharge emission wavelengthmay be used. According to the embodiments, for example, a pressure curvewhen the substrate processing apparatus 2 is vacuum-exhausted as shownin FIG. 3 can be obtained by using the partial pressure sensor 60.

A process flow of the leak check step according to the embodiments willbe described with reference to FIGS. 4, 7 and 8. In the process flowshown in FIGS. 4, 7, and 8, the controller 100 controls the operationsof the components of the processing apparatus 2.

As shown in FIG. 4, the wafer charge step (“WAFER CHARGING” shown inFIG. 4) and the boat loading step (“BOAT UP” shown in FIG. 4) areperformed as a step of loading the boat 26 supporting the plurality ofthe wafers including the wafer W into the process furnace 14. Then,after the wafer charge step and the boat loading step are performed, thevacuum pump 52 vacuum-exhausts the inner atmosphere of the processfurnace 14 until the inner pressure of the process furnace 14 reachesand is maintained at a predetermined pressure (vacuum level) (“1STVacuum-exhaust” shown in FIG. 4), and the heater 12 heats the processfurnace 14 until the temperature of the wafer W in the process furnace14 reaches and is maintained at a predetermined temperature(“temperature stabilizing” shown in FIG. 4).

Thereafter, when the inner temperature of the process furnace 14 isstabilized, the leak check step is subsequently performed. That is, theleak check step is performed before the film-forming process which isthe substrate processing for processing the wafer W. In the leak checkstep, a step of measuring the residual oxygen after the vacuum-exhaustby the partial pressure sensor 60 provided in the exhaust pipe 46, and astep of comparing the measured partial pressure value of the oxygen(also simply referred to as an “oxygen partial pressure value”) with athreshold value are performed. Then, when the oxygen partial pressurevalue exceeds the threshold value, at least one among an N₂ purge (“N₂PURGE” shown in FIG. 4) and an evacuation (“2^(ND) VACUUM-EXHAUST” shownin FIG. 4) is performed. Further, in order to compare the oxygen partialpressure value of the residual oxygen after the vacuum-exhaust with thethreshold value, the oxygen partial pressure value and the thresholdvalue are compared at a pressure (for example, a reference vacuumpressure) at which a residual gas is likely to be generated due to theoxidation of the wafer W.

In the leak check step, the partial pressure of the oxygen or the oxygencompound is measured by the partial pressure sensor 60 provided inaddition to the pressure sensor 48 (“LEAK CHECK (TOTAL PRESSURE)” shownin FIG. 4), and the measured oxygen partial pressure value is comparedwith the threshold value (“OXYGEN PARTIAL PRESSURE CHECK” shown in FIG.4). Thereby, it is determined whether or not the subsequent step (thatis, the film-forming step) can be performed. Then, when the measuredoxygen partial pressure value does not fall under the pre-set thresholdvalue, the N₂ purge by supplying the N₂ gas (that is, the inert gas)into the process furnace 14 is performed, or the evacuation, which isvacuum-exhausting (or evacuating) the inner atmosphere of the processfurnace 14 through the exhaust pipe 46, is performed, or both of the N₂purge and the evacuation are performed. The leak check step describedabove is repeatedly performed until the oxygen partial pressure valuemeasured by the partial pressure sensor 60 is equal to or lower than thethreshold value.

Subsequently, the N₂ purge and the evacuation (also referred to as a“vacuum-exhaust”) will be described with reference to FIG. 2. Theevacuation refers to exhausting the inner atmosphere of the processfurnace 14 until the inner pressure of the process furnace 14 reachesand is maintained at the reference vacuum pressure (also referred to asa “reference pressure”). In the present specification, the referencevacuum pressure refers to a minimum pressure that can be reached when asucking amount of a vacuum pump such as the vacuum pump 52 becomes zero.In FIG. 2, the vacuum pump (“PUMP” shown in FIG. 2) is operated with avalve (“AV” shown in FIG. 2) closed and the valve (“APC” shown in FIG.2) open. Further, the N₂ purge may be performed by supplying the N₂ gaswith the valve AV open and exhausting the inner atmosphere of theprocess furnace 14 by operating the vacuum pump PUMP. The N₂ purge maybe performed while storing the purge gas (that is, the N₂ gas) with thevalve AV open and the valve APC closed to elevate the inner pressure ofthe process furnace 14.

Subsequently, the leak check step will be described in detail withreference to FIG. 7. In the leak check step, first, the inner pressureof the process furnace 14 is detected by the pressure sensor 48 whileevacuating (vacuum-exhausting) the inner atmosphere of the processfurnace 14. When the inner pressure of the process furnace 14 is equalto or lower than a predetermined pressure, the oxygen partial pressureis detected by the partial pressure sensor 60. The predeterminedpressure refers to a pressure determined in advance according to thespecifications of the partial pressure sensor 60, and the predeterminedpressure according to the present embodiments is about several tens ofPascal (Pa).

When the reference vacuum pressure reached by evacuating the inneratmosphere of the process furnace 14 is higher than the predeterminedpressure, the process flow proceeds to a purge step (“PURGE” shown inFIG. 4) without detecting the oxygen partial pressure by the partialpressure sensor 60 and without performing the film-forming step(“FILM-FORMING” shown in FIG. 4). By performing the purge step, theinner atmosphere of the process furnace 14 is replaced with the inertgas such as the N₂ gas and the inner pressure of the process furnace 14is returned to the atmospheric pressure. As described above, when theinner pressure of the process furnace 14 is higher than thepredetermined pressure even when the inner pressure of the processfurnace 14 is evacuated to reach the reference vacuum pressure, there isa high possibility that the leak has occurred in the process furnace 14.

Further, when the detection of the oxygen partial pressure by thepartial pressure sensor 60 is started at the predetermined pressure andthe inner pressure of the process furnace 14 reaches the pressure atwhich the residual gas is likely to be generated due to the oxidation ofthe wafer W, it is determined whether or not the oxygen partial pressurevalue measured by the partial pressure sensor 60 is less than thethreshold value. When the oxygen partial pressure value measured by thepartial pressure sensor 60 is less than the threshold value, it isdetermined that the subsequent step can be performed, and thefilm-forming step of processing the wafer W is performed.

Further, when the oxygen partial pressure value measured by the partialpressure sensor 60 is equal to or higher than the threshold value, themeasurement of the oxygen partial pressure value by the partial pressuresensor 60 is interrupted, and the inner atmosphere of the processfurnace 14 is purged (N₂ purged) until a target pressure (for example,an arbitrary pressure equal to or higher than the predeterminedpressure) is reached. The target pressure may be set as desired, and maybe a pressure smaller than the predetermined pressure. Then, theevacuation of the inner atmosphere of the process furnace 14 isrestarted from the target pressure and then the predetermined pressureis reached, the measurement of the oxygen partial pressure value by thepartial pressure sensor 60 is restarted. Then, when the reference vacuumpressure is reached, the oxygen partial pressure value measured by thepartial pressure sensor 60 and the threshold value are re-compared.

As a result of the comparison, when the oxygen partial pressure valuemeasured by the partial pressure sensor 60 is less than the thresholdvalue, it is determined that the subsequent step can be performed, andthe film-forming step of processing the wafer W is performed. As aresult of the comparison, when the oxygen partial pressure value ishigher than the threshold value, the measurement of the oxygen partialpressure value by the partial pressure sensor 60 is interrupted, and itis determined that the number of times of comparing the oxygen partialpressure value with the threshold value has reached a predeterminednumber of times. When it is determined that the number of times ofcomparing the oxygen partial pressure value with the threshold value hasnot reached the predetermined number of times, the inner atmosphere ofthe process furnace 14 is purged again until the target pressure isreached. As described above, even when the oxygen partial pressure valueis equal to or higher than the threshold value, the inner atmosphere ofthe process furnace 14 may be repeatedly purged and evacuated up to thepredetermined number of times. When the oxygen partial pressure value isless than the threshold value even after comparing the oxygen partialpressure value with the threshold value the predetermined number oftimes, the process flow proceeds to the purge step (“PURGE” shown inFIG. 4), and the leak check step is forcibly terminated.

FIG. 8 schematically illustrates a modified example of the leak checkstep shown in FIG. 7. In the following description, features of themodified example different from those of the leak check step shown inFIG. 7 will be described in detail below, and the description offeatures of the modified example the same as those of the leak checkstep shown in FIG. 7 will be omitted or simplified.

First, the detection of the oxygen partial pressure by the partialpressure sensor 60 is started at the predetermined pressure whileevacuating (vacuum-exhausting) the inner atmosphere of the processfurnace 14. Then, the residual oxygen when the reference vacuum pressureis reached is measured by the partial pressure sensor 60, and themeasured oxygen partial pressure value is compared with the thresholdvalue. When the oxygen partial pressure value measured by the partialpressure sensor 60 is less than the threshold value, the process flowproceeds to the film-forming step. On the other hand, when the oxygenpartial pressure value measured by the partial pressure sensor 60 ishigher than the threshold value, the measurement of the oxygen partialpressure value by the partial pressure sensor 60 is interrupted. Then,it is determined whether or not the number of times of comparing theoxygen partial pressure value with the threshold value is twice or more.Since t number of times of comparing the oxygen partial pressure valuewith the threshold value is once, the inner atmosphere of the processfurnace 14 is purged (N₂ purged) until the inner pressure of the processfurnace 14 reaches the target pressure. When the inner pressure of theprocess furnace 14 reaches the target pressure again, the oxygen partialpressure value is measured by the partial pressure sensor 60, and theoxygen partial pressure value measured by the partial pressure sensor 60at the reference vacuum pressure and the threshold value are re-comparedwhile evacuating (vacuum-exhausting) the inner atmosphere of the processfurnace 14. When the oxygen partial pressure value is less than thethreshold value, the process flow proceeds to the film-forming step, andthe leak check step is terminated.

As a result of the re-comparison, when the oxygen partial pressure valueis equal to or higher than the threshold value, it is determined whetheror not the number of times of comparing the oxygen partial pressurevalue with the threshold value is twice or more. When the number oftimes of comparing the oxygen partial pressure value with the thresholdvalue is twice or more, it is determined whether or not the oxygenpartial pressure value measured by the partial pressure sensor 60 isbeneficially reduced. For example, when the oxygen partial pressurevalue is higher than the threshold value but less than the oxygenpartial pressure value in the previous comparison, the controller 100determines that the oxygen partial pressure value is beneficiallyreduced.

Specifically, as a result of the re-comparison, when the oxygen partialpressure value is equal to or higher than the threshold value and theoxygen partial pressure value remains unchanged from or becomes higherthan the oxygen partial pressure value in the previous comparison, themeasurement of the oxygen partial pressure value by the partial pressuresensor 60 is stopped, the process flow proceeds to the purge step, andleak check step is terminated. Then, the purge step (“PURGE” shown inFIG. 4) is performed such that the inner atmosphere of the processfurnace 14 is replaced with the inert gas and the inner pressure of theprocess furnace 14 is returned to the atmospheric pressure. On the otherhand, when the oxygen partial pressure value is equal to or higher thanthe threshold value and the oxygen partial pressure value isbeneficially reduced to be smaller than the oxygen partial pressurevalue in the previous comparison, the measurement of the oxygen partialpressure value by the partial pressure sensor 60 is interrupted, and theinner atmosphere of the process furnace 14 is purged (N₂ purged) untilthe target pressure is reached while detecting the inner pressure of theprocess furnace 14 by the pressure sensor 48. Then, the evacuation ofthe inner atmosphere of the process furnace 14 is performed again. Whenthe reference vacuum pressure is reached, the oxygen partial pressurevalue measured by the partial pressure sensor 60 and the threshold valueare compared. As described above, in the process flow shown in FIG. 8,while it is determined whether or not the oxygen partial pressure valueis beneficially reduced, the purge to the target pressure and theevacuation from the target pressure to the reference vacuum pressure arerepeatedly performed until the oxygen partial pressure value reaches thethreshold value.

In the substrate processing, as described above, the wafer W in theprocess furnace 14 is processed by performing the film-forming process(that is, the source gas supply step, the source gas exhaust step, thereactive gas supply step and the reactive gas exhaust step). Then, whenthe film-forming process is completed, the inner atmosphere of theprocess furnace 14 is replaced with the N₂ gas and purged (“PURGE” shownin FIG. 4), and then the boat unloading step (“BOAT DOWN” shown in FIG.4), a wafer cooling step (“WAFER COOLING” shown in FIG. 4) and the waferdischarging step (“WAFER DISCHARGING” shown in FIG. 4) are performed asa step of unloading the processed wafers including the wafer W out ofthe process furnace 14.

Subsequently, the threshold value used in the leak check step will bedescribed.

As shown in FIG. 5, the threshold value used in the leak check step isset based on an oxidation degree of a wafer under the film-formingconditions acquired in advance. For example, it is possible to determinethe oxidation degree of the wafer by obtaining a sheet resistance valueof the wafer after processing the wafer on which a titanium nitride(TiN) film is formed. That is, the threshold value refers to a valuedetermined in advance by a relationship between the oxygen partialpressure value acquired in advance and the sheet resistance value of thewafer on which the TiN film is formed. The relationship between theoxygen partial pressure value and the sheet resistance value can bedetermined by preparing a test wafer including the wafer on which theTiN film is formed and obtaining the sheet resistance value when thetest wafer is loaded into the process furnace 14.

Specifically, it is possible to derive a correlation between an amountof a minute leak (that is, an amount of the partial pressure of theresidual oxygen or the oxygen compound) and the oxidation degree of thewafer by conducting experiments with a configuration shown in FIG. 6.According to the configuration shown in FIG. 6, a line 34 a ofintroducing the oxygen or the air is provided on a gas supply side ofthe substrate processing apparatus 2, and a needle valve 34 b capable ofcontrolling a minute flow rate is provided on the line 34 a at alocation immediately before where the gas is introduced into the processfurnace 14. By adjusting an opening degree of the needle valve 34 b, itis possible to change the partial pressure of the residual oxygen or theoxygen compound to generate a minute leak state. Then, by changing thepartial pressure of the residual oxygen or the oxygen compound, the TiNtest wafer is heat-treated for monitoring the oxidation degree of thewafer under each condition. Then, the correlation between the partialpressure of the residual oxygen (or the oxygen compound) and theoxidation degree of the wafer is obtained from the resulting sheetresistance value. As described above, the threshold value of the partialpressure of the residual oxygen or the oxygen compound can be determinedby the specified sheet resistance value of the TiN test wafer.

(4) Effects According to Present Embodiments

According to the present embodiments, it is possible to provide at leastone or more of the following effects.

(a) According to the present embodiments, the partial pressure of thegas such as the residual gas and a desorbed gas in the process furnace14, which causes the wafer W to be oxidized before the film-forming stepis performed, can be measured. Therefore, it is possible to morereliably check the conditions of the process furnace 14 before thefilm-forming step is performed. As a result, it is possible to suppressthe oxidation of the wafer W during the film-forming step, and it isalso possible to consistently maintain the quality of the substrateprocessing.

(b) According to the present embodiments, an absolute amount (that is,the partial pressure) of the residual gas or the desorbed gas in theprocess furnace 14 related to the oxidation of the wafer can be adjustedfor each batch. As a result, it is possible to measure the partialpressure of the desorbed gas in the process furnace 14 before thefilm-forming step, which cannot be measured by the conventional leakcheck based on measuring the leak amount. Therefore, it is possible tosuppress the oxidation of the wafer W during the film-forming step, andit is also possible to consistently maintain the quality of thesubstrate processing.

(c) According to the present embodiments, by comparing the thresholdvalue and the partial pressure of the residual gas (that is, the oxygenpartial pressure value) under a decompressed environment (for example,under the reference vacuum pressure) at which the residual gas is likelyto be generated due to the oxidation of the wafer, it is possible tomore accurately grasp the conditions of the process furnace 14 beforethe film-forming step is performed. As a result, it is possible tosuppress the oxidation of the wafer W during the film-forming step, andit is also possible to consistently maintain the quality of thesubstrate processing.

(d) According to the present embodiments, the threshold value isdetermined by the measured value when the TiN test wafer used to checkthe conditions after the maintenance of the process furnace 14 istransferred into the process furnace 14. Therefore, it is possible tomore accurately grasp the conditions of the process furnace 14 beforethe film-forming step is performed. As a result, it is possible tosuppress the oxidation of the wafer during the film-forming step, and itis also possible to consistently maintain the quality of the substrateprocessing.

(e) According to the present embodiments, by repeatedly performing thepurge (N₂ purge) and/or the evacuation (vacuum-exhaust) while measuringthe partial pressure of the residual gas (that is, the oxygen partialpressure value) under the decompressed environment (for example, underthe reference vacuum pressure) at which the residual gas is likely to begenerated due to the oxidation of the wafer, it is possible to maintainthe process furnace 14 in a clean condition. As a result, it is possibleto suppress the oxidation of the wafer W during the film-forming step,and it is also possible to consistently maintain the quality of thesubstrate processing.

(f) According to the present embodiments, by repeatedly performing thepurge (N₂ purge) and/or the evacuation (vacuum-exhaust), it is possibleto perform the substrate processing after the process furnace 14 isbrought into a clean condition. As a result, it is possible to reducethe lot rejection (lot-out) due to the stoppage of the processing.

(g) According to the present embodiments, a setup operation of thesubstrate processing apparatus can be performed without using the TiNtest wafer to check the conditions of the process furnace 14 after themaintenance and without using the TiN test wafer checking batch.Therefore, it is possible to improve the efficiency of the setupoperation, and it is also possible to increase a utilization rate of thesubstrate processing apparatus. Further, an external leak can be easilychecked without using a He leak detector after the maintenance of theprocess furnace 14. Therefore, it is possible to improve the efficiencyof the setup operation, and it is also possible to increase theutilization rate of the substrate processing apparatus.

Other Embodiments

While the technique is described in detail by way of the embodiments,the above-described technique is not limited thereto. Theabove-described technique may be modified in various ways withoutdeparting from the gist thereof.

For example, the above-described embodiments are described based on thesubstrate processing apparatus used in the manufacturing processes ofthe semiconductor device and the method of manufacturing thesemiconductor device. However, the above-described technique is notlimited thereto. For example, the above-described technique may also beapplied to a substrate processing apparatus such as an LCD (LiquidCrystal Display) manufacturing apparatus configured to process a glasssubstrate and a method of manufacturing the LCD.

Further, as for the film-forming process, the above-described techniquemay also be applied to any process other than the film-forming processdescribed above as long as the inner pressure of the furnace isdecompressed to process the substrate. The above-described technique mayalso be applied to process a film other than the oxide film.

Further, the film-forming process described above may include a processsuch as a CVD (chemical vapor deposition) process, a PVD (Physical VaporDeposition) process, a process of forming a nitride film and a processof forming a film containing a metal.

For example, the above-described embodiment and the modified exampledescribed based on the substrate processing apparatus configured toperform the film-forming process and the method of manufacturing thesemiconductor device. However, the above-described technique is notlimited thereto. For example, the above-described technique may also beapplied to other substrate processing apparatuses such as an exposureapparatus, a lithography apparatus, a coating apparatus and a CVDapparatus using plasma.

According to some embodiments in the present disclosure, it is possibleto measure the partial pressure of the gas, which causes the wafer to beoxidized before the film-forming step is performed, such as the residualgas and the desorbed gas in the process furnace.

What is claimed is:
 1. A method of manufacturing a semiconductor device,comprising: (A) checking a leak from a process furnace before asubstrate is processed, wherein (A) comprises: (a) measuring, by apartial pressure sensor provided at an exhaust pipe, an oxygen partialpressure value of a residual oxygen after the process furnace isvacuum-exhausted; (b) comparing the oxygen partial pressure valuemeasured by the partial pressure sensor with a threshold value; and (c)when the oxygen partial pressure value is higher than the thresholdvalue in (b), performing at least one among: purging the process furnaceand evacuating the process furnace.
 2. The method of claim 1, wherein apressure sensor configured to detect an inner pressure of the processfurnace is provided at the exhaust pipe, and the partial pressure sensoris arranged in vicinity of the pressure sensor.
 3. The method of claim2, wherein (A) further comprises: (d) detecting the inner pressure ofthe process furnace by the pressure sensor while evacuating the processfurnace; and (e) measuring the oxygen partial pressure by the partialpressure sensor when the inner pressure of the process furnace detectedin (d) is equal to or lower than a predetermined pressure.
 4. The methodof claim 3, wherein the partial pressure sensor starts measuring theoxygen partial pressure value by the partial pressure sensor when theprocess furnace is evacuated to the predetermined pressure, and theoxygen partial pressure value when the process furnace is evacuated to areference vacuum pressure is compared with the threshold value in (c).5. The method of claim 4, wherein (A) further comprises: (f) when theoxygen partial pressure value is equal to or higher than the thresholdvalue in (b), performing: (f-1) interrupting measuring the oxygenpartial pressure value by the partial pressure sensor, and purging theprocess furnace until a target pressure is reached; (f-2) restartingevacuating the process furnace and restarting measuring the oxygenpartial pressure value by the partial pressure sensor when the targetpressure is reached; and (f-3) comparing the oxygen partial pressurevalue measured at the reference vacuum pressure with the thresholdvalue, and wherein (f) is performed a predetermined number of times. 6.The method of claim 4, wherein (A) further comprises: (g) counting thenumber of times of comparing the oxygen partial pressure value with thethreshold value; and (h) when the oxygen partial pressure value is equalto or higher than the threshold value and the number of times counted in(g) is once, performing: (h-1) interrupting measuring the oxygen partialpressure value by the partial pressure sensor, and purging the processfurnace until a target pressure is reached; (h-2) restarting evacuatingthe process furnace from the target pressure and restarting measuringthe oxygen partial pressure value by the partial pressure sensor; and(h-3) comparing the oxygen partial pressure value measured at thereference vacuum pressure with the threshold value.
 7. The method ofclaim 6, further comprising: (D) purging the process furnace such thatan inner atmosphere of the process furnace is replaced with an inert gasand the inner pressure of the process furnace is returned to anatmospheric pressure when the oxygen partial pressure value is equal toor higher than the threshold value, the number of times counted in (g)is twice or more and the oxygen partial pressure value remains unchangedfrom or becomes higher than a previous value of oxygen partial pressure,wherein (D) is performed after stopping measuring the oxygen partialpressure value by the partial pressure sensor.
 8. The method of claim 6,wherein (A) further comprises: (i) when the oxygen partial pressurevalue is equal to or higher than the threshold value, the number oftimes counted in (g) is twice or more and the oxygen partial pressurevalue is lower than a previous value of oxygen partial pressure,performing: (i-1) interrupting measuring the oxygen partial pressurevalue by the partial pressure sensor, and purging the process furnaceuntil a target pressure is reached; (i-2) restarting evacuating theprocess furnace from the target pressure and restarting measuring theoxygen partial pressure value by the partial pressure sensor; and (i-3)comparing the oxygen partial pressure value measured at the referencevacuum pressure with the threshold value.
 9. The method of claim 8,wherein (A) further comprises: (j) when the oxygen partial pressurevalue is equal to or higher than the threshold value, the number oftimes counted in (g) is twice or more and the oxygen partial pressurevalue is equal to or lower than the previous value of oxygen partialpressure, performing: (j-1) purging the process furnace until the targetpressure is reached; (j-2) restarting evacuating the process furnacewhen the target pressure is reached; and (j-3) comparing the oxygenpartial pressure value measured at the reference vacuum pressure withthe threshold value, wherein (j-1), (j-2) and (j-3) are performed untilthe oxygen partial pressure value becomes lower than the threshold valueby the oxygen partial pressure value being reduced.
 10. The method ofclaim 3, further comprising: (B) purging the process furnace such thatan inner atmosphere of the process furnace is replaced with an inert gasand the inner pressure of the process furnace is returned to anatmospheric pressure without measuring the oxygen partial pressure bythe partial pressure sensor when the inner pressure of the processfurnace detected in (d) is higher than the predetermined pressure afterthe process furnace is evacuated to a reference vacuum pressure.
 11. Themethod of claim 1, further comprising: (C) processing the substrate,wherein (C) is performed when the oxygen partial pressure value is lowerthan the threshold value in (b).
 12. The method of claim 1, wherein thethreshold value is determined in advance by a relationship between theoxygen partial pressure value acquired in advance and a sheet resistancevalue of a substrate on which a titanium nitride film is formed.
 13. Themethod of claim 12, wherein the relationship between the oxygen partialpressure value and the sheet resistance value is determined by a sheetresistance value when a test substrate comprising the substrate on whichthe titanium nitride film is formed is transferred into the processfurnace.
 14. A non-transitory computer-readable recording medium storinga program that causes, by a computer, a substrate processing apparatusto perform: (A) checking a leak from a process furnace before asubstrate is processed, wherein (A) comprises: (a) measuring, by apartial pressure sensor provided at an exhaust pipe, an oxygen partialpressure value of a residual oxygen after the process furnace isvacuum-exhausted; (b) comparing the oxygen partial pressure valuemeasured by the partial pressure sensor with a threshold value; and (c)when the oxygen partial pressure value is higher than the thresholdvalue in (b), performing at least one among: purging the process furnaceand evacuating the process furnace.